2 Replies Latest reply on Jun 21, 2012 2:07 AM by robert.white

    Stimulus signal problem

    robert.white

      Hi,

       

      I am a student researching signal integrity and I am new to Hyperlynx SI, so this question may have a simple answer:

       

      When stimulating various nets, for crosstalk investigation, on a PCB design (I am using BoardSim) with different signals, I seem to get strange results,

       

      eg:

       

      D1 is stimulated with a signal.

      D2 & D3 are the aggressor nets, and are being stimulating with different signals

       

      When I simulate this , the signals on D2 & D3 are shown to be the same as the signal on D1.

       

      This was carried out by stimulating the signals per net, however, when I used the 'stimulated per pin' option, I got the results I expected(ie signals on D2 & D3 are different from D1).  I am wondering why this is happening??

       

      I do not know if this is either a problem with the way I am stimulating the signals, or if my understanding of 'stimulating per net' is wrong??

       

      Anything that can clear up the difference between the two stimulate settings: 'Per Net' & 'Per Pin', would be greatly appreciated.

       

      Cheers

       

      Robert

        • 1. Re: Stimulus signal problem
          weston_beal

          The different stimuli must be assigned at the net or pin level as you intend to use them. If you assign a stimulus to a net, then whatever pin is the driver on that net uses that stimulus unless overridden with a pin-level stimulus assignment. It sounds like you assigned stimulus patterns at the pin level, so the other drivers on the net use the default stimulus.

          • 2. Re: Stimulus signal problem
            robert.white

            Thanks for clearing up the difference, however this does not seem to be the problem.

             

            The stimulus patterns being set on the nets are causing me the problems. I have set either stimulus at net OR stimulus at pin(clearing to default before changing where I stimulate signals), not both, so I do not think I can be overridding the net stimulus.

             

            Just to be clear, D1, D2 & D3 are all seperate nets, with seperate drivers.

             

            Is there another reason that D2 & D3 appear the same as D1?

             

            Cheers

             

            Robert